0-1背包问题（java）.txt

来自「背包问题动态规划算法JAVA 给定n种物品和一背包。物品i的重量是wi」· 文本 代码 · 共 60 行

class Knapsack
  {
  public static void knapsack(int[] v, int[] w, int c, int[][] m)
      {
      int n = v.length-1;
      int jMax = Math.min(w[n]-1, c);
      for(int j = 0; j <= jMax; j++)
         
        m[n][j] = 0;           
      for (int l = w[n]; l <= c; l++)
      m[n][l] = v[n]; 
      for(int i = n-1; i >=1; i--)
      {
         jMax = Math.min(w[i]-1,c);
                 
          for(int k = 0; k <=jMax; k++)
              m[i][k] = m[i+1][k];
                       
               for(int h = w[i]; h <= c; h++)
           m[i][h] = Math.max(m[i+1][h],m[i+1][h-w[i]]+v[i]);
        }
        m[0][c] = m[1][c];
          if(c >= w[0])
            m[0][c] = Math.max(m[0][c],m[1][c-w[0]]+v[0]);
                  System.out.println("bestw ="+m[0][c]);
            }
          
  public static void traceback(int[][] m, int[] w, int c, int[] x)
           {
               int n = w.length-1;
               for(int i = 0; i<n;i++)
                 if(m[i][c] == m[i+1][c]) x[i] = 0;
                    else {x[i] = 1;
                           c -= w[i];}
                                             
               x[n] = (m[n][c]>0)?1:0;}
  public static void main(String[] args)
  {
  int[] ww = {2,2,6,5,4,5};
  int[] vv = {6,3,5,4,6,8};
  int    n=5;
  int    c=13;
  int[][] mm = new int[c+1][c+1];
  knapsack(vv,ww,c,mm);
    
     int[] xx =new int[ww.length];
     traceback(mm,ww,c,xx);
     for(int i = 0;i<xx.length;i++)
       System.out.println("x["+i+"]="+xx[i]);
     for(int i=0;i<n;i++)
       {
       	for(int j=0;j<=c;j++)
          System.out.print("m["+i+","+j+"]="+mm[i][j]+" ");          
          
          System.out.println();
         }
          
          }
     
  }